WASHINGTON — Additional weapons that Navy SEALs and Green Berets desperately need to defend themselves in far-flung outposts in Afghanistan apparently are being delayed, according to documents and officials familiar with the equipment.

At issue is a mortar system that uses a computer to drop explosives quickly and accurately on enemy fighters who assault small forts. Insurgents with rocket-propelled grenades can outgun American special operations forces there. An urgent plea for 20 of the mortar systems was approved by the Joint Chiefs of Staff in January, yet no new weapons have been sent as of late September.

The Pentagon says it is "in the process of acquiring and fielding the additional numbers."

In January 2010, commanders made their first request for such a weapon. By April 2011, nine Enhanced Mortar Targeting Systems had been sent to Navy SEALs, Army Green Berets, Marine special operations forces and regular Army units to protect the remote outposts where they trained local Afghan forces. In July 2011, the mortar system killed its first enemy fighter, and in November 2011, it had helped repel an attack on Combat Outpost Margah in eastern Afghanistan.

A defense official familiar with the system but not authorized to speak on the record said he fears the request won't be filled quickly until an outpost gets overrun. The systems can be built in about seven months with commercially available technology, he said.

Documents show the military realizes the urgency. A budget description says that U.S. troops at remote locations "can be overwhelmed" and that bad weather or restrictive use on dropping bombs may prevent aircraft from providing them with protection. The enhanced mortar has filled that niche, according to the document, but the next step is not to send more to Afghanistan. Rather, it is to "integrate the system" with an Army software program.

Commanders want more of the fast, deadly mortars, and in January 2012, a Joint Urgent Operational Need Statement — the process to speed badly needed gear to troops in combat — was approved by the Joint Chiefs of Staff. That request remains classified, but the Pentagon acknowledges that it seeks 20 additional EMTAS mortar systems. They cost about $300,000 apiece.

In a statement to USA TODAY, the Pentagon said it will begin buying the systems "within the next few weeks" once funds become available. Fighting generally diminishes rapidly in Afghanistan in the fall as the weather turns colder.

The Pentagon acknowledges the need, saying an assessment of the mortar "concluded that the system provided a rapid, accurate capability" to hit insurgents while avoiding civilian casualties and reducing "risk to U.S. operating forces."

A statement from the office of the Joint Chiefs of Staff said the urgent request was being handled appropriately.

The Joint Chiefs "wouldn't say that there has been a delay," the statement said. "This requirement is currently on track within the acquisition process."

Loren Thompson, a defense analyst at the Lexington Institute and a consultant to military contractors, said the military has improved its ability to field equipment to troops in Iraq and Afghanistan. But it's still not fast enough.

"This case illustrates why you can't supply urgent wartime needs through the normal purchasing process," Thompson said. "It's too slow, and as a result lives are put at risk."